Recent advances in optical fiber technology have promoted the use of these light conducting elements as promising alternative media in the transmission of information signals. Typically, such fibers are light-transparent glass threads on the order of 0.01 inch or less in diameter encased in a sheath or cladding to which it is fused. Light enters one end of the fiber and emerges from the opposite end with minimal loss. The physics of light transmission through a continuous fiber is now well-understood and need not be considered in detail for an understanding of the invention. As in its electrical counterpart, light transmission for broad circuit application requires some means for switching between one light transmission path and two or more other such paths. This has long been readily accomplished in the transmission of electrical signals by providing electromechanical relay or switch means which are interposed in the circuits to be controlled. The electrical conductors of the circuits are simply soldered or otherwise connected to the relay or switch terminals. The switching of light transmission paths which include optical fibers has been accomplished more directly. Known optical switching arrangements have generally contemplated the coupling of the actual light conducting media themselves without intervening contacting or circuit completion apparatus. Switching of light transmission paths thus has involved the mechanical movement of the end of the actual conducting fiber itself out of alignment with the end of a second fiber and into alignment with the end of a third fiber. One such prior art switching arrangement is disclosed in U.S. Pat. No. 4,223,978 of R. B. Kummer et al., issued Sept. 23, 1980. In the arrangement there disclosed, four passive fibers are fixedly maintained in the four corners of a square cross-sectioned inner channel of a rigid sleeve. An active fiber extends through a flexible, second sleeve fitted over the rigid sleeve and is arranged so that one end of the active fiber is moveable in a plane parallel to the plane of the ends of the passive fibers. The flexible sleeve may then be manually or machine flexed in either direction along two perpendicular axes to selectively bring the active fiber into alignment with the four passive fibers.
In another somewhat similar switching arrangement described in an article entitled "Mechanical Optical-Fibre Switch," by P. G. Hale et al., in Electronics Letters, Vol. 12, No. 15, July 22, 1976, the active fiber is fitted with a magnetically responsive metallic sleeve. The active fiber is then moved into selective alignment with the passive fibers by magnetic forces generated by an external electromagnet acting on themetallic sleeve. In each of the foregoing and other switching arrangements, the problem of achieving a precise optical connection between two fiber ends is presented. The ends of the extremely thin fibers must be in precise alignment without offset to achieve light transfer between the fiber ends. In order to minimize loss, the fiber ends must also be in extremely close proximity or actually abutting. These requirements demand that after a passive fiber of a plurality of passive optical fibers has been selected, the active fiber be precisely moved into coupling therewith. It is to these objectives that the optical switch apparatus of the invention is chiefly directed.